Boys and Girls Affected Equally

Though many doctors believe that boys with ADHD are much more likely to develop these problems than girls, Biederman says his study shows that just isn't so.

"The picture of ADHD is almost identical among the genders," he says. Regardless of gender, it's advisable to screen kids with ADHD for other conditions.

Brad Reimherr, MD, associate professor of psychiatry at the University of Utah, isn't surprised. He says his own study of adult sufferers of ADHD shows that women are even more impaired than men.

"Both in terms of symptoms of hyperactivity and attention deficit itself and also in terms of other emotional ailments, women were more likely to have problems," Reimherr tells WebMD.

Part of the problem, he agrees, is that society thinks of ADHD as a male disorder. Males act out more and tend to get more attention.

Females -- regardless of age -- are more apt to be misdiagnosed, typically with anxiety or depression, he says. As a result, the condition often goes untreated, even though studies show that women respond well to ADHD medications, Reimherr says.

More Than 1 in 5 Act Out

The study, presented at the annual meeting of the American Psychiatric Association, included 235 teenage girls, about half of whom had ADHD. Their average age was 17.

About nine in 10 had received treatment for their disorder, usually a combination of drugs and counseling, Biederman says.

On almost every measure, the ADHD sufferers fared worse than their unafflicted counterparts:

More than 20% were disruptive vs. 3% of those without ADHD.

More than one in three suffered major depression, compared with three in 100 of those without ADHD.